Clinically amyopathic dermatomyositis manifested after the allogeneic haematopoietic stem cell transplantation: Case presentation and literature review.

Clinically amyopathic dermatomyositis (CADM) lacks muscle symptoms, associated with rapidly progressive interstitial lung disease. Anti-melanoma differentiation-associated gene 5 (MDA-5) antibody has been identified as a disease-labelling autoantibody. We report two cases of CADM manifested after the allogeneic haematopoietic stem cell transplantation (allo-HSCT)-Case 1: a 56-year-old man with acute leukaemia received the allo-HSCT and Case 2: a 45-year-old female patient with lymphoma received the allo-HSCT. She received donor lymphocyte infusion because of a post-transplant relapse. After allo-HSCT or donor lymphocyte infusion, Gottron papules emerged, and both patients were diagnosed as CADM based on dermatological findings coupled with the positivity of anti-MDA-5 antibody, accompanied by interstitial shadows consistent with ILD on chest computed tomography. Case 2 was initially diagnosed as a kind of chronic graft versus host disease. Their symptoms were improved by the combination of immunosuppressive agents with a concomitant decrease in anti-MDA-5 antibody levels. For Case 2, rituximab was subsequently started for relapse of lymphoma, resulting in a substantial decrease in the level of anti-MDA-5 antibody and improvement in rash and ILD. Our cases raise a possibility that CADM emerges after the HSCT, highlighting the importance of early diagnosis to avoid fated progression into ILD.